Rotation-slide bearing

ABSTRACT

The invention relates to a rotation-slide bearing ( 25   c ) which comprises an inner first bearing element ( 31 ) with an outer peripheral surface ( 31   a ) and an outer second bearing element ( 32 ) with an inner peripheral surface ( 32   a ). The outer bearing element ( 32 ) encloses the inner bearing element ( 31 ). At least one first oil groove ( 38 ) that extends in an approximately axial relation is provided in the outer peripheral surface ( 31   a ) of the inner first bearing element ( 31 ) and/or in the inner peripheral surface ( 32   a ) of the outer second bearing element ( 32 ). In order to improve a rotation-slide bearing of the aforementioned kind in such a way that it can absorb radial and axial forces and has good slide properties, a support shoulder ( 42   a   , 42   b ) with a slide surface ( 42   c ) is associated with one of the two bearing elements ( 31 ) on one or both sides and axially supports the bearing element ( 32 ) with its lateral surface ( 32   c ) facing it. At least one second oil groove ( 32   c ) that extends in an approximately radial relation is disposed in the slide surface ( 42   c ) or in the lateral surface ( 32   c ) supported by it. The oil grooves ( 46   a   , 46   b   , 38 ) communicate in the zone where they face one another.

The invention relates to a rotary plain bearing, particularly for adrive shaft of an axial-piston machine.

In the majority of cases, shafts transmit torques, in which case theyare subject mainly to radial loads and have to be mounted in radialbearings. At the same time, almost unavoidable axial forces occur andthese can be taken by an axial bearing for the shaft. In an axial-pistonmachine, its shaft is subject to quite considerable axial loads, becausethe axially acting forces from the pistons are transmitted to the shaft.For this reason, the drive shaft of an axial-piston machine has to bemounted in load-carrying bearings both radially and axially.Rolling-element bearings or plain bearings may be used for this purpose.Rolling-element bearings are notable for being particularly free-runningbecause, due to the rolling friction, their frictional losses are low.The load-bearing capacity of a rolling-element bearing on the other handis relatively small, because the pressure per unit area on the rollingelements is high. In a plain bearing on the other hand, there is arelatively large area available for the sliding movement that occurs andthe pressure per unit area can thus be kept relatively low. Plainbearings are thus particularly suitable for heavy bearing loads.

To keep the friction and wear in a plain bearing low, it is known fromDE 43 36 915 A1 for wedge-shaped lubricant pads to receive a lubricantto be arranged in one of two mutually adjacent slide faces. No flow ofthe lubricant takes place through the lubricant pads.

The object underlying the invention is to design an existing rotaryplain bearing in such a way that it is able to withstand radial andaxial forces and has good sliding properties.

This object is achieved by virtue of the features of claim 1.Advantageous refinements of the invention are described in thesubclaims.

In the rotary plain bearing according to the invention, one of the twobearing elements has associated with it, on one or both sides, a supportshoulder having a slide face against which the other bearing element issupported axially by its side face adjacent the support shoulder. Also,lubricating grooves are arranged radially between the bearing elementsand axially between one bearing element and the adjacent supportshoulder or shoulders, the at least one radially extending lubricatinggroove and the at least one approximately axially extending lubricatinggroove in the mutually adjacent surface regions being connectedtogether. This produces a combined radial and axial bearing which issimple and small in construction, something which is achieved by thecombined design. The rotary plain bearing according to the invention maybe so arranged in this case that it is supported axially in only oneaxial direction or in both axial directions and is in the form of anaxial bearing. For this reason, the rotary bearing according to theinvention is also suitable as a so-called fixed bearing which, is ableto withstand axial and radial forces and can be arranged in combinationwith an axially spaced away, so-called loose bearing which withstandsonly radial forces.

Due to the presence of the lubricating grooves according to theinvention, the rotary plain bearing according to the invention is welllubricated in operation in respect of both radial and axial forces, thusreducing friction and wear and giving the bearing a long working life.Due to the radial, or rather radially ascending, path followed by the atleast one lubricating groove between the support shoulder and thebearing element supported thereby, there is produced, in operation, whenthe lubricating groove is arranged in the rotating bearing element anddue to the centrifugal force that acts on the lubricant, a pumping orfeeding action which operates automatically and which causes thelubricant to leave the lubricating groove in a radially outwarddirection and fresh lubricant to enter it radially on the inside, e.g.through the lubricating clearance that exists or through a specialinfeed opening or infeed passage. It is not only the approximatelyradially extending lubricating groove which benefits from this automaticoutfeed and infeed of lubricant but also the approximately axiallyextending one, if it is connected to the first groove.

A forced-feed action on the lubricant in the approximately axiallyextending lubricating groove can be obtained if this lubricating grooveis obliquely arranged. When this is the case, the slide face which is insliding contact with the lubricant exerts on the lubricant a componentof feeding force which is directed in the longitudinal direction of thelubricating groove, the direction of action being dependent on thedirection of rotation and on whether the lubricating groove is situatedin the rotating or non-rotating element of the bearing.

The feeding action which has been described above can be made forced inthe region of the at least one approximately radially extendinglubricating groove if the lubricating groove is so inclined that thelubricant situated in the groove is fed outwards as a result of thesliding contact with the slide face of the adjoining element acting as acomponent of force. If the lubricating groove is arranged in the elementwhich rotates in operation, it is advantageous for the lubricatinggroove to be inclined in the opposite direction to the direction ofrotation. If on the other hand the lubricating groove is arranged in theelement which does not rotate, it is advantageous for the lubricatinggroove to be inclined in the direction of rotation of the adjoiningrotating element to obtain the forced-feed action described above. Thisaction can be obtained in two lubricating grooves arranged on the twosides of the bearing element concerned if the lubricating grooves areinclined in opposite directions to one another and are connectedtogether, preferably by an axially or obliquely extending lubricatinggroove. The inner bearing element is preferably supported by at leastone lateral support flange.

Other features of refinements of the invention relate to the mounting ofthe other, and particularly the outer or second, bearing element to havelimited mobility as in a ball-joint. The latter can be obtained byforming the second bearing element to have, arranged in a transverseplane, a circumferential surface in the form of a section of a sphere bywhich it is seated in a recess in the form of a concave section of asphere in a third bearing element or a wall of a housing. In addition tothe axial support on at least one side, this produces a rotary plainbearing capable of movement as in a ball-joint which compensates formisalignments resulting from bending of the associated shaft, and thusprotects the bearing from wear and overloading.

Other refinements of the invention relate to improving the rotary plainbearing in respect of its ability to be fitted and stripped out and toobtaining designs which are simple, small and reliable and having a longworking life.

Advantageous embodiments of the rotary plain bearing according to theinvention will be explained in detail below by reference to thedrawings. In the drawings:

FIG. 1 is an axial section through an axial-piston machine.

FIG. 2 is an enlarged cross-sectional view of the detail marked II inFIG. 1 which includes a rotary plain bearing according to the invention.

FIG. 3 is a partial section on III-III in FIG. 2.

FIG. 4 is a perspective, partly cut-away, view of a rotary plain bearingaccording to the invention as a unit assembly.

FIG. 5 shows the rotary plain bearing of FIG. 4 in a different operatingposition.

FIG. 6 shows the rotary plain bearing in a pre-assembly position.

FIG. 7 is an axial section through an outer element of the rotary plainbearing.

FIG. 8 is an axial section through a modified embodiment of rotary plainbearing

FIG. 9 is an axial section through an embodiment of rotary plain bearingwhich has been further modified.

FIG. 10 is an axial section through an embodiment of rotary plainbearing which has been further modified.

FIG. 11 is a view in axial section of a modified embodiment of rotaryplain bearing according to the invention.

FIG. 12 is a perspective view of a second and a third element of therotary plain bearing.

FIG. 13 is an end-on view of a portion of the rotary plain bearing.

FIG. 14 is an enlarged cross-sectional view of the detail marked XIV inFIG. 1, containing a modified embodiment of plain bearing according tothe invention.

The piston machine shown in FIG. 1, which is of a design shown by way ofillustration and which is denoted as a whole by reference numeral 1, hasa housing 2, in whose interior 3 a swash-plate 4 and a cylindrical drum5 are arranged next to one another. Arranged in the cylindrical drum 5,distributed around the circumference thereof, are holes 6 for pistons,which holes 6 extend, in the present embodiment of axial-piston machine,substantially parallel to a centre axis 7 of the cylindrical drum 5 andare open at the end-face 5 a of the cylindrical drum 5 which is adjacentthe swash-plate 4. Firmly inserted in the bushed holes 6, preferably bybeing pressed in, are guide bushes 8.

Mounted in the guide bushes 8 to be displaceable substantially axiallyare pistons 9, which are preferably cylindrical and whose heads form theboundaries, in the direction of the swash-plate 4, of working chambers11 in the cylindrical drum 5. The foot-ends of the pistons 9, which areadjacent the swash-plate 4, are each supported on the swash-plate 4 by ajoint 12, in which case there may be slide-shoes 13 present, betweenwhich and the foot-ends the joints 12 are arranged, which joints 12 arepreferably in the form of ball-joints having a ball-head and a sphericalrecess.

The end-face of the cylindrical drum 5 which is remote from theswash-plate 4 rests against a control disc 14 in which are arranged atleast two control openings 15 in the form of kidney-shaped through-holeswhich form parts of an infeed duct 16 and an outfeed duct 17 which aremerely indicated and which extend through an adjacent wall 18 of thehousing against which the control disc 14 is held. The cylindrical drum5 is arranged on a drive shaft 19 which is rotatably mounted in thehousing 2 and whose axis of rotation 21 extends coaxially to the centreaxis 7 of the cylindrical drum 5.

In the present embodiment, the housing 2 is made up of a cup-shapedhousing part 2 a having an end-wall 2 b and a circumferential wall 2 cand of a cover or connecting part 2 d which forms the wall 18 of thehousing and which rests against the free edge of the circumferentialwall 2 c and is screwed thereto by screws 22 which are merely indicated.To connect up with the infeed and outfeed ducts 16, 17 which run onoutwards, pipe connections 16 a, 17 a are provided on the connectingpart 2 d. The drive shaft 19, which passes through the cylindrical drum5 in a mounting bore, is rotatably mounted and sealed in bearingseatings in the housing end-wall 2 b and in the cover 2 d by means ofsuitable bearings 25, 25 a, and in this case it passes through thehousing end-wall 2 b axially and has a stub drive-end 19 a whichprojects from the housing end-wall 2 b.

In this embodiment where the piston machine 1 is in the form of aswash-plate machine, the cylindrical drum 5 is arranged on the driveshaft 19 to be solid in rotation therewith by means of a rotaryentrainment connection 26, e.g. a toothed coupling, with the drive shaft19 passing through the swash-plate 4, which is arranged in a fixedposition on the housing end-wall 2 or is formed thereon, in athrough-hole 27. In the present embodiment, the cylindrical drum 5rotates relative to the swash-plate 4 in working operation, the pistons9 being moved longitudinally towards the working chambers 11 and backagain.

In the embodiment, the rear bearing 25 a, which is mounted in thehousing wall 18, i.e. in the connecting part 2 d, is a rotary plainbearing 25 b which is combined with a rotary plain bearing 25 c capableof motion as in a ball-joint, thus enabling it to mount the drive shaft19 in such a way as to be rotatable and also to compensate forshortcomings in the alignment of the bearings 25, 25 a and/or forbending of the drive shaft 19 which occurs in working operation. Thisprevents or reduces tipping at the rotary plain bearing 25 b, whichimproves the sliding action, reduces friction and heating-up in therotary plain bearing 25 d and extends its working life.

The rotary plain bearing 25 c which is capable of motion as in aball-joint and which is combined in the manner described above has aninner first bearing element 31 having an outer first slide face 31 a bywhich it is rotatably mounted with a sliding clearance in an outersecond bearing element 32 having an inner second slide face 32 a.Consequently, the outer second bearing element 32 surrounds the innerfirst bearing element 31, the outer second bearing element 32 being, atleast at its outer circumference, in the form of a ring having an outerthird bearing surface 32 b in the form of a zone of a sphere, by whichsurface 32 b it is made capable of limited mobility as in a ball-joint.What this means is that it is mounted in such a way that it can betilted in all directions in relation to the axis of rotation 21, in athird bearing element 33 having an inner fourth bearing surface 33 awhich is at least partly in the shape of a corresponding section of asphere.

In the embodiment, the second bearing element 32 and the third bearingelement 33 are in the form of rings, which may for example be of thesame width b axially. In the embodiment, the first bearing element 31 iswider than the second and third bearing elements 32, 33 and projectsbeyond them on, for example, both sides.

In the embodiment, the first bearing element 31 is also formed by abearing sleeve 31 b, preferably of hollow cylindrical cross-section,which is arranged on a stub mounting end 19 a of the drive shaft 19 tobe solid in rotation therewith, e.g. is a press-fit on the stub mountingend 19 a.

The third bearing element 33 is preferably also a bearing sleeve 33 b,which is mounted in or on the part carrying it in such a way as to befixed in rotation, it being mounted on the cover or connecting part 2 din this case. Provided for this purpose in the latter is a bearing bore34 for the round third bearing element 33, which bore 34 preferably hasa shoulder face 34 a formed by an interior step, which face 34 a formsan outer stop for the third bearing element 33 in the axial direction.In the embodiment, the bearing bore 34 extends inwards beyond theinterface 2 e between the connecting part 2 d and the control disc 14and into the latter, there preferably also being a shoulder face 34 barranged at this point, which forms an inwards stop for the bearingelement 33, by which means it is positively located axially. In thisembodiment, the bearing sleeve 33 b forms a centering spigot to centrethe control disc 14.

The embodiments shown in FIGS. 1 to 9 and 11 to 13 are set up for rotarymovement between the first and second bearing elements 31, 32 and formovement as in a ball-joint or tilting movement between the second andthird bearing elements 32, 33. To prevent rotary movement about the axisof rotation 21 between the second and third bearing elements 32, 33,there is provided between the second and third bearing elements 32, 33 arotation-blocking arrangement 35 which operates by positiveinterengagement and which has a spigot connection. The spigot connectioncomprises a blocking spigot 35 b which projects from one of the twobearing elements 32, 33 and engages in a slotted hole 35 a in the otherbearing element 32, 33, the slotted hole 35 a extending longitudinallyon the axis of rotation 21. The slotted hole 35 a and the blockingspigot 35 b are also situated in that radial plane Er of the relevantbearing element 32, 33 which contains the centre of curvature M.Consequently, rotary movement between the bearing elements 32, 33 isblocked but a limited tilting movement in all directions, which permitsthe compensating action described above, is possible.

The blocking spigot 35 b may be formed by a round pin 35 c which issecurely mounted in a bore in one of the bearing elements 32, 33, e.g.is pressed thereinto, and whose projecting, e.g. thickened, head engageswith clearance for movement in the slotted hole 35 a in the otherbearing element 32, 33. In the embodiment, the hole for the pin isarranged in the second bearing element 32 and the slotted hole 35 a isarranged in the third bearing element 33.

The blocking spigot 35 b is preferably arranged in the longitudinalcentre plane E which symmetrically intersects the control openings 15,or in longitudinal centre plane E1 which extends perpendicularlythereto. This is because the sum of the forces from the pistons exerts aresultant transverse force on the drive shaft 19 which acts in thelongitudinal centre plane E and which, being a torque, may cause thedrive shaft 19 to bend slightly, which is compensated for by a tiltingmovement in the longitudinal centre plane E. The bearing 25 c capable ofmovement as in a ball-joint is able to perform this tilting movement inall transverse directions without any problems, particularly when theslotted hole 35 a extends in the longitudinal centre plane E or evenwhen it is situated in the longitudinal centre plane E1. When it is inthis position, a tilting movement as described above takes place aboutthe transversely extending centre axis of the blocking spigot 35 b.

The third bearing element 33 has on one side an axial insertion groove36 whose transverse dimensions A, B and whose cross-sectional shape arearranged to be larger than the axial cross-sectional shape and size ofthe second bearing element 32, thus enabling the latter to be insertedin the insertion groove 36 in a position in which it is rotated throughan angle, e.g. a position in which it is rotated through an angle of90°. The axial length 36 of the insertion groove 36 is made sufficientlylarge for the second bearing element 32 to be able to be slid in it toan intermediate position shown in FIG. 5 in which the centres ofcurvature of the third and fourth bearing surfaces 32 a, 33 a aresituated on the common centre of curvature M and thus coincide with oneanother. In this position, the second bearing element 32 can be turnedto its final position in which its longitudinal centre axisapproximately lines up with the longitudinal centre axis of the thirdbearing element 33. In this turned-back position, the second bearingelement 32 is positively located axially in the third bearing element 33by the undercut in the fourth bearing surface 33 a which is in the formof a section of a sphere.

In the embodiment, there are two insertion grooves 36 arranged indiametrically opposed positions as mirror images of one another, thusenabling the second bearing element 32 to be inserted centrally into thethird bearing element 33. The floor faces 36 a of the insertion grooves36, which floor faces 36 a are situated opposite one another and arepreferably rounded in cross-section to match the diameter D of thesecond bearing element 32, are preferably arranged to be tangential tothe fourth bearing surface 33 a in the form of a section of a sphere,which means that they end centrally in the third bearing element 33 andmerge with the fourth bearing surface 33 a in the form of a section of asphere. This has the particular advantage that the second bearingelement 32, when being inserted, finds stops for the movement by whichit is being inserted on those portions of the fourth bearing surface 33a in the form of a section of a sphere which are situated axiallyopposite the insertion grooves 36, and does so in the intermediateposition in which the centres of curvature coincide with one another andthe second bearing element 32 is rotatable. This ensures that fitting iseasy and convenient as far as manipulation is concerned. The secondbearing element 32 only needs to be moved as far as an insertion stopand then turned.

In the embodiment, the width B of the at least one insertion groove 36is approximately k to h of the diameter D of the second bearing element32. When it is of this size, there are, as well as the at least oneinsertion groove 36, sufficiently large portions of the fourth bearingsurface 33 a in the form of a section of a sphere to provide thepositively engaging undercut in the axial direction.

A press-fit between the circumference of the third bearing element 33and the wall of the bearing bore 34 may be used to lock the thirdbearing element 33 in rotation in the wall 18 of the housing. In theembodiment shown in FIG. 8, in which the same or comparable parts aregiven the same reference numerals, there is also a rotation-blockingarrangement 37 acting by positive interengagement, in the form of aspigot connection, provided to lock the third bearing element 33 inrotation in the wall 18 of the housing, i.e. in the connecting part 2 d.What preferably serves this purpose is the blocking spigot 35 b, whichpasses through the third bearing element 33 and engages in a slottedhole 37 a in the wall 18 of the housing, which slotted holes 37 asubstantially corresponds to the slotted hole 35 a. In this embodiment,not only the second bearing element 32 but also the third bearingelement 33 is positively located at the wall 18 of the housing to stoprotation in the circumferential direction.

The second bearing element 32 is fitted, and the blocking spigot 35 b isinserted in the slotted hole 35 a, by inserting the second bearingelement 32 in a position in which it, and the blocking spigot 35 b, isrotated relative to the slotted hole 35 a sufficiently far (FIG. 6) forthe blocking spigot 35 b to be able to be inserted in the insertiongroove 36. When the blocking spigot 35 b is in the region of the slottedhole 35 a, the second bearing element 32 is rotated back, and when thisis done the blocking spigot 35 b enters the slotted hole 35 a. This canbe done without any problems because of the second bearing element 32being in the shape of a section of a sphere.

Given suitable sizing, it is even possible in the case of the embodimentshown in FIG. 8 for the elongated blocking spigot 35 b to be inserted inthe slotted holes 35 a, 37 a, which is done by inserting the secondbearing element 33 in a rotated position and then rotating it back, inthe way that has already been described for the embodiment shown inFIGS. 2 to 6. It is however also possible for the slotted hole 37 a toopen towards the side from which the third bearing element 33 can beslid into the bearing bore 34. In this embodiment, the third bearingelement 33, with the second bearing element 32 mounted in it, can beslid into the bearing bore 34, and the blocking spigot 35 b is insertedin the slotted hole 37 a at the same time. In the embodiment shown inFIG. 8, this is possible from the inner side, because the slotted hole37 a opens towards the interface 2 e between the wall 18 of the housingand the control disc 14 and the rotary plain bearing 25 c capable ofmovement as in a ball-joint can be fitted to the control disc 14 priorto the control disc 14 being mounted against the wall 18 of the housingor prior to the wall 18 of the housing being mounted against the controldisc 14.

In the embodiment shown in FIG. 9, in which the same or comparable partsare given the same reference numerals, a different form 37 of therotation-blocking arrangement is provided, in which case therotation-blocking arrangement 35 may be of the form shown in FIG. 8. Asshown in FIG. 9, the rotation-blocking arrangement 37 is likewise formedby a spigot connection but the connection is arranged not transverselyto the axis of rotation 21 but parallel thereto and is formed by ablocking pin 37 c which is arranged in the region of the step face andengages in holes situated opposite one another in the wall 18 of thehousing and in the third bearing element 33.

The embodiment shown in FIG. 10, in which the same or comparable partsare likewise given the same reference numerals, makes it clear thatthere is no need for a separate third bearing element 33 if the innerfourth bearing surface 33 a and the at least one insertion groove 36 areformed directly in the wall 18 of the housing, i.e. in the connectingpart 2 d. In this embodiment too, blocking arrangements as shown in FIG.8 or FIG. 9 may be provided, in which case the slotted hole 35 a may bearranged in the wall 18 of the housing (though this is not shown).

In the present piston machine or axial-piston machine 1, there ispresent in the interior 3 hydraulic fluid, e.g. hydraulic oil, which, inworking operation, may be used to lubricate the slide faces 31 a, 32 aand preferably the bearing surfaces 32 b, 33 a too. A water-containinglubricant liquid which contains approximately 50% water andapproximately 50% glycol and which is known to the trade by the name HFCis particularly suitable as a lubricant liquid.

To ensure access for the lubricant liquid situated in the interior 3,particularly to the rotary plain bearing 25 b, it is advantageous for anaxial through-passage 14 a which provides access for the lubricantliquid at least to the rotary plain bearing 25 b to be provided betweenthe control disc 14 and the drive shaft 19. In the embodiment, thecontrol disc 14 has a through-hole which surrounds the drive shaft 19 atan annular distance. The diameter D1 of the through-hole is preferablylarger than the outside diameter of the first bearing element 31 or thebearing sleeve 31 b, thus ensuring annular access to the slide faces 31a, 33 a and preferably also to the bearing surfaces 32 b, 33 a.

To further improve the lubrication, it is advantageous for one or morelubricating grooves 38, which are arranged to be distributed around thecircumference and which may extend axially, or obliquely or helically,as shown in FIGS. 2 to 7, to be provided in at least one of the slidefaces 33 a, 32 a, this being done in the inner second slide face 32 a inthe present case. If the at least one lubricating groove 38 is arrangedto be oblique or helical, there is produced on each axial side of thesecond bearing element 32 a load-bearing region B1 which is defined bythe associated edge of the lubricating groove 38 and an axiallyextending slide face line 39.

In the embodiments described above, the rotary plain bearing 25 c iswhat is called a loose bearing in relation to the drive shaft 19, i.e.there is no mutual axial support between the drive shaft 19, or ratherthe first bearing element 32 which is arranged in a fixed positionthereon, and the second bearing element 32. There is on the other handaxial support of this kind between the third bearing element 33 and thehousing 2 or rather the wall 18 of the housing which holds the rotaryplain bearing 25 b. However, there are also types of operation in whichit is desirable for there to be axial support between the first andsecond bearing elements 31, 32 in at least one axial direction. This canbe achieved by setting a limit for the second bearing element 32 on oneor both sides by means in each case of a shoulder or slide face which isarranged on the drive shaft 19 or an added part. A rotary plain bearingof this kind which is a fixed bearing in at least one axial directioncan be formed as a rotary plain bearing 25 b having two bearing elements31, 32 or as a tiltable rotary plain bearing 25 c having the second andthird bearing elements 32, 33 and can thus withstand axial forces in oneor both axial directions.

In the embodiment shown in FIG. 11, in which the same or comparableparts are given the same reference numerals, the rotary plain bearing 25c is arranged in the region of the housing 2, in the housing end-wall 2b in the present case, in the form of a fixed bearing operative in bothaxial directions, in which case it may form the bearing 25 a arranged inthe connecting part 2 d or, preferably, the bearing 25 arranged in thehousing end-wall 2 b, as shown in FIG. 11. With clearance for movement,a limit is set for the second bearing element 32 at both end-faces by asupport flange 42 a, 42 b, which is fixed axially on the drive shaft 19or the first bearing element 31. In the embodiment, one support flange,the outer support flange 42 a in the present case, is connected in onepiece to the first bearing element 31, with these items forming anangled annular body, and the inner support flange 42 b has a co-axialhole 43, by the edge of which hole it is mounted on the drive shaft 19with a small amount of clearance for movement. On the side remote fromthe rotary plain bearing 25 c, the support flange 42 b may be supportedaxially by a shoulder 44 on the drive shaft which, in the embodiment, isformed by a spring ring which fits into an annular groove in the driveshaft 19. The first bearing element 31 preferably extends to that faceof the second support flange 42 b which is adjacent to it, and in theother axial direction, in the outwards direction in the present case, itis supported axially by a shoulder 45 on the drive shaft, which shoulder45 may project in one piece from the drive shaft 19 as an annularflange.

For lubrication purposes, there are provided in each of the shoulder orslide faces 42 c of the support flanges 42 a, 42 b (not shown) or ineach of the end-faces 32 c of the second bearing element 32, one or morelubricating grooves 46 a, 46 b which are arranged to be distributedaround the periphery, which extend from the inside outwards, and whichare connected in the radially inward direction to a lubricant infeedduct and in the radially outward direction to a lubricant outfeed ductand are thus part of a lubricant circuit 47 through which a lubricant,e.g. hydraulic oil, flows when the piston machine is operating. Aspecial lubricant pump is not required to maintain the flow in thelubricant circuit 47. The lubricant which is present in the lubricatinggrooves 46 a, 46 b in operation produces the flow in the circuit 47automatically as a result of the centrifugal force acting on it. Thelubricant circuit 47 may for example be connected to the interior 3 ofthe housing 2.

An additional feeding action on the lubricant can be obtained when thelubricating grooves 46 a, 46 b are inclined, and particularly when thelubricating grooves 46 a on one side and the lubricating grooves 46 b onthe other side are inclined in opposite directions to one another. Thelubricating grooves 46 a (not shown) situated in the rotating bearingelement, in the support flanges 42 a, 42 b in the present case, may beinclined in the opposite direction to the direction of rotation of therotating bearing element, or the lubricating grooves 46 a, 46 b situatedin the non-rotating bearing element, in the second bearing element 31 inthe present case, may be inclined in the direction of rotation. Theinclination may also be of a spiral form. In these embodiments, aforced-feed action on the lubricant is created by the contact betweenthe slide faces, i.e. the support flanges 42 a, 42 b in the presentcase, and the columns of lubricant situated in the lubricating grooves46 a, 46 b. In the embodiment, in which the lubricating grooves 46 a, 46b are arranged in the non-rotating second bearing element 32, theforced-feed action is created by the contact which is made by the slidefaces 42 c of the rotating first bearing element 31, which latter isformed by the support flanges 42 a, 42 b.

In the embodiment, mutually associated lubricating grooves 46 a, 46 bwhich are arranged on the two sides of the second bearing element 32 areconnected to the at least one lubricating groove 38, which may besituated in the outer circumferential surface of the first bearingelement 31 or in the inner circumferential surface of the second bearingelement 32 and may extend axially in this case, as is shown in FIGS. 4and 5 for example, or may extend obliquely, as is shown in FIG. 7 forexample. If the lubricating groove 38 follows an oblique path, theforced-feed action is also created in the region of the lubricatinggroove 38. The feeding action is produced by the contact which the slideface, which is adjacent the lubricant in the at least one lubricatinggroove 38, makes with the lubricant. The lubricating grooves 46 a, 46 bwhich are connected by the straight lubricating groove 38, or thelubricating grooves 46 a, 46 b which are connected by an obliquelubricating groove 38, and also the oblique lubricating groove 38, areorientated in such a way that the feeding action operates in successivedirections and a feeding action which is continuous in the sections oflubricating groove 46 b, 38, 46 a results. In operation, the lubricantthen enters at the radially outer end of the lubricating groove orgrooves on one side and exits at the radially outer end of thelubricating groove or grooves on the other side. The axial path followedby the feeding action and the outward or inward direction of feed dependon the direction of rotation of the drive shaft 19 or of the firstbearing element 31.

In the embodiment, the lubricant circuit 47 is formed by having thelubricant grooves 46 b on the inside open to the interior 3 in aradially outward direction. The lubricating grooves 46 a on the outsideare likewise open in a radially outward direction and may likewise beconnected to the interior 3, by a lubricant passage (not shown).

FIG. 11 shows an embodiment in which pivot-bearing lubrication for apivotable swash-plate 4 which is known per se is included in addition inthe lubricant circuit 47. In this embodiment, the lubricant grooves 46 aopen radially outwards into a preferably annular gap or section oflubricant passage 47 a from which there extends, in the housing end-wall2 b, a lubricant passage 47 b which continues, e.g. at an angle, to theplain bearing surface 48 of a pivot bearing 49 for the swash-plate 4which, in this embodiment, is pivotably mounted, the passage 47 bpassing through, as it continues, a bearing shell 51 of the pivotbearing 49. The pivot bearing 49 which is arranged at the other end ofthe piston machine 1 in relation to the axis of rotation 7 of the driveshaft 19 can be connected to the lubricant circuit 47 in the same way,but for reasons of simplicity this has not been shown.

In the embodiment, the directions of flow of the flow in the circuit inthe region of the rotary plain bearing 25 c are directed, starting fromthe openings of the lubricant passages 46 b, first radially inwards,then axially outwards and then radially outwards, see S1, S2, S3.

FIG. 13 shows the lubricant grooves 46 a, 46 b inclined in mutuallyopposed directions on the two sides of the second bearing element 32.

In the embodiment shown in FIG. 12, an axially operative anti-rotationlocking means 37 is formed by having one or more, e.g. two, sectors 37 dsituated in opposite positions to one another project axially from theannular body of the third bearing element 33, which sectors 37 dco-operate by positive interengagement, for the purpose of anti-rotationlocking, with locating recesses which are arranged directly orindirectly in the housing 2 or its end-wall 2 b and in which the sectors37 d engage, or with one or more locating spigots which engage in the atleast one recess 37 e which exists between two sectors.

In the embodiment, the third element 33 of the rotary plain bearing 25 cis seated in a bearing bore 61 which has on the inside an abutmentshoulder 62 for the third bearing element 33 and which, towards theoutside, widens in a stepped shape, a closure ring 64 having a ring seal65 for the drive shaft 19 being inserted in the larger step 63 of thebore and being secured axially by a circlip 66.

In the embodiment shown in FIG. 14, in which the same or comparableparts are once again given the same reference numerals, axial support isproduced for the second bearing element 32 as shown in FIG. 11 in arotary plain bearing 25 b which is not capable of movement as in aball-joint and whose outer second bearing element 32 is cylindrical inform and is inserted in a matched bearing bore 61, e.g. in the housingend-wall 2 b. Otherwise, including the position and design of thesupport flanges 42 a, 42 b and the lubrication grooves 46 a, 46 b, theembodiment shown in FIG. 14 corresponds to that shown in FIG. 11, to thewhole of which the reader is referred, for which reason any freshdescription can be omitted.

1. Rotary plain bearing (25 c), particularly for a drive shaft (19) of apiston machine, and preferably an axial-piston machine (1), which has aninner first bearing element (31) having a circumferential surface (31 a)and an outer second bearing element (32) having an inner circumferentialsurface (32 a), the outer bearing element (32) surrounding the innerbearing element (31), wherein at least one first lubricating groove (38)which extends through continuously and approximately axially is providedin the circumferential surface (31 a) of the inner first bearing element(31) and/or in the inner circumferential surface (32 a) of the outersecond bearing element (32), wherein one of the two bearing elements(31) has associated with it, on one or both sides, a support shoulder(42 a, 42 b) having a slide face (42 c) against which the bearingelement (32) is supported axially by its side face (32 c) adjacent thesupport shoulder (42 a, 42 b), wherein at least one approximatelyradially extending second lubricating groove (46 a, 46 b) is arranged inthe slide face (42 c) or in the side face (32 c) supported thereagainst,and wherein the lubricating grooves (46 a, 46 b, 38) are connected toone another in the region where they are mutually adjacent.
 2. Rotaryplain bearing according to claim 1, characterised in that, on at leastone side of the bearing element (31) or (32), the at least onelubricating groove (46 a, 46 b) is inclined in a circumferentialdirection.
 3. Rotary plain bearing according to claim 2, characterisedin that lubricating grooves (46 a, 46 b) which are inclined in oppositedirections to one another are arranged on the two sides.
 4. Rotary plainbearing according to one of the foregoing claims, characterised in thatthe lubricating groove (38) extends obliquely.
 5. Rotary plain bearingaccording to one of the foregoing claims, characterised in that thelubricating grooves (46 a, 46 b, 38) are part of a flow circuit (47)which is preferably connected to the interior (3) of the piston machine.6. Rotary plain bearing according to one of the foregoing claims,characterised in that the or one of the two support shoulders (42 a) isconnected in one piece to one bearing element, and in particular to thefirst bearing element (31).
 7. Rotary plain bearing according to one ofthe foregoing claims, characterised in that a support shoulder (42 b) isformed by a separate annular disc which is preferably mounted on thedrive shaft (19).
 8. Rotary plain bearing according to one of theforegoing claims, characterised in that the outer bearing element (32)is formed to have, on its outer circumference, a third bearing surface(32 b) in the form of a section of a sphere, by which it is mounted tohave limited mobility as in a ball-joint in a third bearing element (33)having an inner fourth bearing surface (33 a) in the form of a sectionof a sphere which surrounds the third bearing surface (32 d), and inthat there is arranged on one side of the third bearing element (33) atleast one insertion groove (36) at which the second bearing element (32)can be inserted in the third bearing element (33), in an angularlyrotated position, to a position at which the centres of curvature (M) ofthe third and fourth bearing surfaces (32 b, 33 a) substantiallycoincide with one another.
 9. Rotary plain bearing according to claim 8,characterised in that two insertion grooves (36) are arranged inopposite positions to one another.
 10. Rotary plain bearing according toclaim 9, characterised in that the floor faces (36 a) of the insertiongrooves (36) run tangentially into the fourth bearing surface (33 a) inthe form of a section of a sphere.
 11. Rotary plain bearing according toone of claims 8 to 10, characterised in that the width (B) of theinsertion groove (36) is approximately ⅓ to ½ of the diameter (D) of thesecond bearing element (32) and the width (b) of the second bearingelement (32) is, at least allowing for clearance for movement, smallerthan the width (B) of the insertion groove (36).
 12. Rotary plainbearing according to one of claims 8 to 11, characterised in that arotation-blocking arrangement (35) is arranged between the second andthird bearing elements (32, 33).
 13. Rotary plain bearing according toone of claims 8 to 12, characterised in that the rotation-blockingarrangement (35) is formed by a spigot connection between the second andthird bearing elements (32, 33) and a blocking spigot (35 b) fastened toone bearing element (32) engages, with axial clearance for movement, inan opening in the other bearing element (33) which is preferably formedby an axial slotted hole (35 a).
 14. Rotary plain bearing according toone of claims 8 to 13, characterised in that the third bearing element(33) is a sleeve-like bearing element which is seated in a bearing bore(34) in an additional bearing element.
 15. Rotary plain bearingaccording to claim 14, characterised in that the additional bearingelement is formed by a connecting part (2 d) of a piston machine, and inparticular of an axial-piston machine (1).
 16. Rotary plain bearingaccording to claim 15, characterised in that the sleeve-like bearingelement has a limit set for it on the inner side by a control disc (14)which is arranged on the inside of the connecting part (2 d).
 17. Rotaryplain bearing according to claim 15 or 16, characterised in that acontrol disc (14) is arranged on the inside of the connecting part (2d), an axial through-passage (14 a) for a lubricant liquid beingarranged in the control disc (14) or between the control disc (14) and adrive shaft (19) carrying the first bearing element (31).